New test for dimensional changes in offset papers
Charles G Weber, M. N. V. Geib · Journal of research of the National Bureau of Standards · 1937
Change of dimension of paper is a serious factor in many of its uses, particularly in multicolor offset printing where changes of dimensions cause the greatest difficulty-misregister of prints.The changes are caused by variations in the relative humidity of the surrounding air.To predict the relative constancy of dimensions of papers in use, a method was devised for determining the expansivity of paper with variations in relative humidity.Specimens of paper approximately 24 inches in length are mounted under constant tension in a cabinet in which humidity is controlled by salt solutions.Changes of length of the paper are measured by means of an optical lever, with a sensitivity of 0.00025 inch and the humidity and temperature inside the cabinet are determined with a wet-and dry-bulb hygrometer.The data thus obtained checked closely with those obtained by measuring specimens on a flat surface with a micrometer rule and were much more conveniently obtained and more reproducible.